Abstract 1040 Human Milk Poster Symposium, Sunday, 5/2

..As a first step to evaluate whether breast-feeding protects against ETEC diarrhea in an endemic area, we measured antibody titers to several ETEC adhesins and to ETEC heat-labile enterotoxin (LT) in human milk samples obtained from lactating Egyptian women. The study was conducted in 2 rural villages in the Nile delta, 40km from Alexandria, Egypt. During a house to house survey, each of 118 lactating women provided a breast milk sample and fecal specimen. At the time of specimen collection, demographic data and a 3-day diarrhea history were also taken. Breast milk total IgA (mcg/ml) and specific titers against LT and colonization factor antigen I (CFA/I), coli surface antigens CS1 through CS4, and CS6 were measured by ELISA. Specific antibody levels were presented as the reciprocal of the geometric mean titer (GMT). Maternal fecal specimens were cultured for bacterial pathogens and presence of ETEC was determined by testing 5 E. coli colonies for LT or heat-stable enterotoxin (ST) expression. Enterotoxin positive E. coli were tested for colinization factors by immunoblot methods.

..The majority of breast milk specimens had detectable titers (≥5) to ETEC antigens ranging from a high of 100% (CS2) to a low of 67% (LT). Reciprocal GMT for all antigens were low and ranged from 5 to 17. Antigen-specific titers were significantly correlated (r = +.23 to +.73) for all antigen pairs. Six mothers had diarrhea of undetermined etiology. One mother with diarrhea had outlying titers to LT (550), CFA/I (100), CS1 (53), CS2 (211), CS3 (355), CS4 (51), and CS6 (32). Compared to titers for mothers without diarrhea, the five remaining mothers with diarrhea had higher reciprocal GMTs against CFA/I (50 vs. 14 p<.05) and CS4 (40 vs. 6, p<.001). Two mothers without diarrhea were infected with ST-only, CF-negative ETEC. For these 2 subjects, antigen-specific titers were not significantly elevated from the population mean. Surrogate variables for increased risk of ETEC exposure including older maternal age, maternal illiteracy, household poverty, and poor household sanitation were not predictive of titer levels.

..In this study, antibodies to each of the ETEC antigens were detectable in the majority of milk samples, but mean titers were low even for common ETEC antigens like LT. In the presence of non-ETEC diarrhea, some titers increased substantially. Still, women presumed to be at higher risk of diarrhea because of their sociodemographic characteristics did not have higher titers possibly implying only transient elevations for titer levels following exposure. Interestingly, antigen-specific titer levels were positively correlated with each other. These correlations may make it difficult to isolate the efficaciousness of one ETEC-specific antibody from another. These findings have implications for studying the role of mucosal antibodies and protection against ETEC diarrhea in an endemic setting.